Tubular connection with helically extending torque shoulder

ABSTRACT

A tubular connection includes a pin member and a box member. The pin member has a first thread structure and a helical torque shoulder spaced axially along the pin member from the first thread structure. The box member has a second thread structure and a second helical torque shoulder spaced axially along the box member from the second thread structure. The first thread structure and the second thread structure are sized and located to control a stab position of the tubular connection, and in the stab position the first helical torque shoulder does not engage or axially overlap with the second helical torque shoulder. A method of joining tubular members utilizing a helical torque shoulder is also provided.

CROSS-REFERENCES

This application claims the benefit of U.S. Provisional Application Ser.No. 61/730,720, filed Nov. 28, 2012, the entirety of which isincorporated herein by reference.

TECHNICAL FIELD

The present application is directed to tubular connections and, moreparticularly, to a tubular connection having a helical torque shoulderarrangement.

BACKGROUND

The Oil & Gas upstream production industry drills wells of everincreasing depth and complexity to find and produce raw hydrocarbons.The industry routinely uses steel pipe (Oil Country Tubular Goods) toprotect the borehole (casing) and to control the fluids produced therein(tubing). Casing and tubing are made and transported in relatively shortlengths and installed in the borehole one length at a time, each lengthbeing connected to the next. As the search for oil and gas has drivencompanies to drill deeper and more difficult wells, the demands on thecasing and tubing have grown proportionately greater in terms of bothtensile and pressure forces. The developing technology of deviated andhorizontal wells have exacerbated this trend, adding to the casing andtubing requirements a further consideration of increasing torsionalloads.

Two general classes of connectors exist within this field. The mostcommon is the threaded and coupled connector, wherein two pin, or malethreads, which are machined on the ends of two long joints of pipe, arejoined by two box, or female threads, machined on a relatively shortmember, a coupling, with a larger outside diameter than the pipe, andapproximately the same inside diameter. The other class is the integralconnector, wherein the pin member is threaded onto one end of afull-length joint of pipe and the box member is threaded into the secondfull-length joint. The two joints can then be directly joined withoutthe need for an intermediate coupling member. The ends of the pipe bodymay be processed further to facilitate the threading of the connection.

A thread profile is generally defined by a thread root, a thread crest,a stab flank, and a load flank as generally shown in FIG. 1. In aconventional thread, the “included angle”, the angle between the loadand stab flanks is positive, meaning that the width of the thread crestis less than the width of the thread groove with which it is initiallyengaged. Hence, the pin tooth is easily positioned into the box grooveas the threads are assembled by rotating one member into the other. Inthe final assembly position, either or both of the crests and roots maybe engaged, and clearance may exist between the load flanks or the stabflanks. This allows the thread to be easily assembled. As reflected inthe exemplary thread position shown in FIG. 2A (stab position), 2B(engaged position) and 2C (fully made-up position), this clearanceavoids the case of the load and stab flanks developing positiveinterference with its mating surface, which would cause the thread to“lock” and not fully engage.

A number of advancements over the years have given rise to “premium”connections. One can generally characterize these connections, comparedto the connections specified by API (American Petroleum Institute) andother like organizations, in that they feature: 1), more sophisticatedthread profiles; 2), one or more metal-to-metal sealing surfaces; and3), one or more torque shoulders. The torque shoulder(s) are a mechanismused to geometrically position the metal seal(s) and to react againstthe threads to resist externally applied torque, while maintainingrelatively low circumferential stress within the threaded section(s) ofthe connection. The torque resistance is a function of the torqueshoulder area.

Another type of thread system that has been used in this field is knownas a “wedge” thread, which is formed by a system of dovetail threads ofvarying width or varying pitch. This type of thread arrangement allowsthreads to easily be engaged and assembled, and yet to develop positiveinterference between opposing flanks of the thread in the fullyassembled position. The wedge thread generally has a greater torqueresistance that other premium threaded connections. The “wedge thread”has certain disadvantages, the principal one being that it is far moredifficult to manufacture and measure than a thread with only a singlepitch. Manufacturing a wedge thread on a taper further increases thedifficulty of both the threading process and the measurement process.

What is needed by the drillers and producers of deep, high-pressure,hot, and/or deviated oil and gas wells is a threaded connection that hashigh-torque characteristics with relative ease of machining andproduction cost.

SUMMARY

In one aspect, a method of joining tubular length of oil country tubularcasing or piping involves the steps of: utilizing a first tubular memberhaving an associated pin member with a first thread structure and afirst helical torque shoulder spaced axially along the pin member fromthe first thread structure; utilizing a second tubular member having anassociated box member with a second thread structure and a secondhelical torque shoulder spaced axially along the box member from thesecond thread structure; engaging the pin member and box member witheach other into a stab position that is defined by interaction of thefirst thread structure and the second thread structure, in the stabposition the first helical torque shoulder does not contact or axiallyoverlap with the second helical torque shoulder; rotating at least oneof the first tubular member or the second tubular member such thatinteraction between the first thread structure and the second threadstructure guides the first helical torque shoulder into cooperatingalignment with the second helical torque shoulder; and continuingrotation of at least one of the first tubular member or the secondtubular member until the first helical torque shoulder fully engageswith the second helical torque shoulder.

In another aspect, a tubular connection includes a pin member and a boxmember. The pin member has a first thread structure and a helical torqueshoulder spaced axially along the pin member from the first threadstructure. The box member has a second thread structure and a secondhelical torque shoulder spaced axially along the box member from thesecond thread structure. The first thread structure and the secondthread structure are sized and located to control a stab position of thetubular connection, and in the stab position the first helical torqueshoulder does not engage or axially overlap with the second helicaltorque shoulder.

In one example, the first thread structure and the second threadstructure may be respective tapered constant pitch threads and the firstand second helical torque shoulder may be formed by respectivenon-tapered structures.

The details of one or more embodiments are set forth in the accompanyingdrawings and the description below. Other features, objects, andadvantages will be apparent from the description and drawings, and fromthe claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic profile of a thread form;

FIGS. 2A, 2B and 2C show a portion of a connection in stab, engaged andmake-up conditions respectively;

FIG. 3 shows an exemplary premium connection with a cylindrical torqueshoulder surface;

FIG. 4 shows an embodiment of a connection with a helical torqueshoulder that runs into a cylindrical torque shoulder;

FIGS. 5 and 6 show another embodiment of a connection with a helicaltorque shoulder that runs into a cylindrical torque shoulder; and

FIG. 7 shows a connection embodiment in which the helical torqueshoulder is formed by a dovetail wedge structure.

FIG. 8 shows an embodiment of FIG. 7 with a variable pitch helicaltorque shoulder.

DETAILED DESCRIPTION

The current tubular connection provides a helical torque shoulderarrangement.

In the primary embodiment, the conventional circumferentially extendingtorque shoulder (e.g., the shoulder normally found at the pin-nose tobox-base of a threaded and coupled premium connection, or a centershoulder) is supplemented or supplanted by a helically extending torqueshoulder.

As aforementioned, most “premium” connections, per the schematic partialpin 10 and box 12 connection shown in FIG. 3, include threads 14, ametal seal 16, and a positive torque shoulder 18. As the first member ofthe connection is assembled into the second, mating member, the threadscontact at some point on their respective “stab” flanks. As the firstmember 10 is rotated into the second, driven by a moment external to themember, the threads engage, and the first member of the threadedconnection moves into the second member, constrained by the geometry ofthe engaged threads. As the thread engagement nears complete assembly,two opposing structures, the “torque shoulders,” contact.

The conventional torque shoulder normally found at the pin-nose tobox-base interface of a threaded and coupled premium connection is acylindrical shoulder surface as represented in FIG. 3, about thecomplete circumference of both members. Both shoulders are eitherlocated in respective planes (e.g., 20) substantially perpendicular tothe longitudinal axis 22 of the member/connection (e.g., in the case ofshoulder surfaces that extend radially only as shown) or alongrespective, relatively narrow axial extents (e.g., axial extent 24, inthe case of shoulders that extend at some angle to the radialdirection). In either case, at any given radial distance from the centeraxis of the member/connection, a circumferentially extending line can bedefined along the surface for that radial distance and the line will liein a plane substantially perpendicular to the axis of the connection. Asthe metal seal surface 16A of the first member contacts the metal sealsurface 16B of the second member, the reaction between the two generatesan opposing force and momentarily arrests the continued axial relativemotion of the threaded members. The threads of the first member, drivenby the external moment, continue to rotate, causing a shift such thatthe thread contact moves from stab-flank engagement to load-flankengagement.

Once the load flanks of the threads are engaged, any increasingadditional externally applied moment causes a reaction between the loadflanks of the thread and the metal to metal seal forcing the firstmember into the second along the path defined by the thread geometry,and further engaging the metal seals, overcoming the resistance of theseals interfering fit. Once the torque shoulder surface 18A of the firstmember contacts the torque shoulder surface 18B of the second member,further rotation is not possible. The contact between each memberstorque shoulders, resists further circumferential movement.

If the external moment is sufficiently large, and the bearing and shearcapacity of the threads sufficiently large, the torque shoulder(s)themselves will yield, the force reacting between the shoulders of eachmember becoming greater than the shear or bearing capacity of theshoulder.

The present disclosure is directed to a solution to increase the torqueresistance of a connection by increasing the surface area of the torqueshoulder, as contact stress is directly proportional to force andinversely proportional to area. For a given pipe wall thickness, thethreads must utilize a certain percentage of the radial depth ofthickness of the wall section to generate the required bearing and sheararea necessary for the threads to transmit the pipe load. The actualpercentage of cross-sectional area is a function of thread geometry:thread pitch, thread height, and thread taper. The remaining portion ofthe radial depth or thickness of the wall section may be used formetal-to metal sealing surfaces and the torque shoulder.

Cold forming the pin nose to reduce the internal diameter of the pinmember enables the designer to increase the torque shoulder surfacearea, but has limitations. One of the most important requirements of OilCountry Tubular Goods is the “drift diameter”, the largest cylinder of aspecified diameter and length that will pass through the assembled tubesand connections. Drift diameter is only slightly smaller than thenominal inside diameter of the pipe body. Hence the pin can only beformed a small amount, limiting the increase in shoulder surface area toa small amount.

In the embodiments illustrated in FIGS. 4-6, the conventional torqueshoulder 30 normally found at the pin-nose to box-base of a threaded andcoupled premium connection is supplemented by a set of helical surfaces32 and 34, machined on a cylindrical section 36 of the tube bodyparallel to its longitudinal axis 38. The pin member 10 helical torqueshoulder has two flanks 32A, 34A, joined by a root and a crest about ahelix of three turns. The box member 12 would have corresponding matingtorque shoulder flanks. Each of these surfaces has the potential to addsurface area to the cylindrical torque shoulder. While the extent ofsurfaces may vary from less than one turn to more than three turns, theprimary issue is finding the surfaces that will support the reaction ofthe primary torque shoulder surfaces 30A and 30B, still cylindrical,against the load flank surfaces of the connection's threads.

In the embodiments illustrated, the helical torque shoulder is in thenature of a trapezoidal “Flank-to-Flank” design. As seen in FIG. 6, thehelical torque shoulder may include start chamfers 50. The box membermay also include a clearance zone 52 between the box metal seal surface16B and the start of the box torque shoulder surface 34B to allow thepin nose and associated start of the pin helical torque shoulder to stabto a location just short (e.g., axially just to the right of in the viewof FIG. 6) of the start of the box torque shoulder surface 34B. Duringassembly, both helically extending flanks/shoulder surfaces of thehelical torque shoulder of one member contact the mating flanks/shouldersurfaces of the helical shoulder of the other member prior to completeassembly (e.g., as the helical torque shoulder on the pin 10 moves intothe helical torque shoulder on the box 12).

The flank surfaces, machined on a mild angle measured from theperpendicular to the longitudinal axis of the pipe body, allow furtherrotation of the connection driven by the externally applied moment. Asthe flank surfaces are driven further together, the normal force betweenthe flank surfaces increases, and the resulting increased force offriction resists the externally applied moment; i.e., it requires agreater moment, torque, to continue to drive the two members together.

As the members are fully assembled, the helical torques shoulder formends and the two cylindrical torque shoulder surfaces engage, greatlyincreasing the assembly torque requirements. Furthermore, once theengaging member is arrested by the perpendicular, cylindrical shoulder,any increasing externally applied moment continues to force a larger andlarger reaction between the load flanks of the helical torque shouldersurfaces and the cylindrical shoulder surfaces.

The reaction between the load flanks of the pin and the load flanks ofthe box results in a compressive force acting on the pin member as theload flanks of the box force the load flanks and the entire pin memberinto the box member. The reaction between the load flanks of the box andthe load flanks of the pin results in a tension force acting on the boxmember as the load flanks of the pin force the load flanks and theentire box member away from the cylindrical torque shoulder.

As the forces increase driven by the increasing external moment,Poisson's effect drives both the pin and box members: diametricallyincreasing the circumference of the pin, which is in compression;diametrically decreasing the circumference of the box, which is intension. This reaction initiates at the cylindrical shoulder surfacesand transfers back the connection, starting with the helical torqueshoulder. Poison's effect locks the helical surfaces, startingimmediately at the intersection of the cylindrical torque shoulder andworking through the helical torque shoulders in the direction of thethreads. This locking mechanism enables both flanks of the helicaltorque shoulder to increase the effective area of the combined torqueshoulder.

This embodiment of the invention offers a number of advantages.

The helical torque shoulder requires only a few helically machinedsurfaces.

The surfaces are similar to thread form, albeit with different function,and can be machined in similar manner to threads.

The helical torque shoulder of the illustrated embodiment is machined ona cylindrical path, parallel to the pipe body longitudinal axis, furthersimplifying both machining and measuring the surfaces. However, in otherembodiments the helical torque shoulder could be machined on a taperedpath.

The engaged surface area may be enlarged by either changing the form(e.g., for thicker-walled tubes, the height of the surfaces may beincreased, or the pitch varied).

Other embodiments of this invention may offer additional orcomplementary advantages. For example, the above description describedtrapezoidal formed surfaces with a mild angle to the perpendicular tothe axis of the tube. Even a mild angle will generate some radialforces. These radial forces will tend to force the two members apart,with the most detrimental effect upon the member with the thinnercross-section; in the embodiment illustrated the pin. An alternateembodiment may use helical surfaces of square or rectangular shape, withthe angle between flank surfaces and the perpendicular to thelongitudinal pipe axis at or near zero.

Other embodiments may use a more complex form, with some flanks havingnegative angles, or dovetail angles. The illustrated helical torqueshoulder follows a cylindrical profile relative to the axis of theconnection, and therefore does not require an axial engagement clearanceas make-up thread forms used in oilfield casing or tubing applicationsdo. Threaded connections must have the characteristic of being able tobe assembled on a drilling rig. This requires some “stabbing” depth tostabilize the length of pipe hanging in the derrick whilst the rigworkers initialize contact between the two members and rotate themtogether. The primary threads 14 in this connection perform thatfunction, whilst the helical torque shoulder need only be optimized toreact to the externally applied moment, the “make-up” torque. Thus, inthe contemplated connection the helical torque shoulder surfaces willnot be engaged or axially overlapped when the two members are in thestab position defined by the primary threads that control the make-upoperation. Only after relative rotation of one member causes axialmovement of the members together will the helical shoulder surfacesbegin to axially overlap and move into each other.

Other embodiments may actually use a variable width form of square,near-square, or dovetail design, in which the flank contact may beenhanced by the wedging mechanisms of the aforementioned wedge thread.Increased torque capacity is a function of the increased surface contactarea of both flanks of the tooth and groove pairs within the wedgedtorque shoulder. This value can be optimized based upon availablesection height and the assembly rotations of the principal driverthreads (the conventional threads located elsewhere in the connection).By way of example, FIG. 7 shows an embodiment in which the helicalshoulder takes on a trapezoidal form that wedges (e.g., as the helicaltorque shoulder 100 of the pin member moves into the helical torqueshoulder 104 of the box member, the shoulders wedge upon full make-up;metal to metal seal is shown at 124).

Torque capacity is also enhanced by any conventional torque shoulderthat may exist within the threaded connection, and should work inconjunction with the helical torque shoulder described above. Aconventional torque shoulder may be an extension of the helical torqueshoulder or be located independently of it, elsewhere within theconnection.

Premium connections have shoulders in different locations, and in somecases, multiple shoulders. The primary locations are:

Pin-Nose/Box-Base, intersecting the inside diameter of the connection(the example given herein).

Pin-Base/Box-Face; i.e., intersecting the outside diameter of theconnection.

The middle-wall section of the connection, the “center shoulder” (e.g.,per shoulder location shown in U.S. Pat. No. 5,415,442, which isincorporated herein by reference).

One skilled in the art will recognize that the concept of a helicaltorque shoulder can be utilized in any and all of these shoulderconfigurations, with appropriate modifications.

Although a metal seal may or may not be present within the threadedconnection, a configuration utilizing a metal-to-metal seal between thehelical torque shoulder and conventional threads will have an additionaladvantage over a conventional premium connection in that the helicaltorque shoulder will isolate the metal-to-metal seal from thecompressive loading experienced by the pin member.

Metal seals are formed by interferingly fitting two smooth metalsurfaces together. During compressive loading, the metal seal,particularly of the pin member, may be deformed because of excessivecompressive loading. Because of the contact pressure produced by theinterference fit, the two surfaces try to separate. Althoughconventional designs use techniques to keep the two surfaces together,analysis shows some degree of separation and resultant loss of contactpressure. The helical torque shoulder will isolate the seal surfacesfrom the effect of axial loads and produce a more stable and consistentmetal seal under a variety of loading conditions.

The helical torque shoulder structures described herein provide a torqueshoulder surface that extends through more than 360 degrees and,preferably through more than 720 degrees. When following the helicalshoulder surface at a given radial distance from the centrallongitudinal axis, the resulting track will not lie within a planesubstantially perpendicular to the longitudinal axis of the pipe orconnection body, or even a narrow extent as suggested in FIG. 3, due thehelical nature of the surfaces.

In one implementation, an axial length L_(HTS) of the helical torqueshoulder may be 30% or less of the overall length L of the connection,while a length of L_(PT) of the primary thread may be about 50% or more(e.g., 60% or more) of the overall length L of the connection, it beingunderstood that the length L of the connection is defined as axialdistance between (i) the shoulder, metal to metal seal or thread locatedfurthest toward one end of the connection and (ii) the shoulder, metalto metal seal or thread located furthest toward an opposite end of theconnection.

In one implementation, the axial length L_(HTS) of the helical torqueshoulder may be between about 15% and 45% of the axial length L_(PT) ofthe primary thread.

In one implementation, the helical torque shoulder extends through nomore than four turns, while the primary thread form extends through atleast ten turns.

It is to be clearly understood that the above description is intended byway of illustration and example only, is not intended to be taken by wayof limitation, and that other changes and modifications are possible.For example, while tapered constant pitch threads of the type used inpremium connections (e.g., per the ULTRA-DQX, ULTRA-FJ, ULTRA-QX andULTRA-SF connections available from Ultra Premium Oilfield Products ofHouston, Tex.) are primarily described in conjunction with the helicaltorque shoulder threads, other types of thread structures could be usedin place of the premium connection threads, such as API Round threads,API Buttress threads or others.

What is claimed is:
 1. A tubular connection, comprising: a pin memberhaving: a first tapered constant pitch thread having a root, a crest, astab flank and a load flank; a first variable pitch helical torqueshoulder surface spaced axially along the pin member from the firsttapered constant pitch thread, the first variable pitch helical torqueshoulder surface being non-tapered; a box member having: a secondtapered constant pitch thread having a root, a crest, a stab flank and aload flank; a second variable pitch helical torque shoulder surfacespaced axially along the box member from the second tapered constantpitch thread, the second variable pitch helical torque shoulder surfacebeing non-tapered; the pin member and the box member configured suchthat in the stab position the first variable pitch helical torqueshoulder surface does not engage or overlap with the second variablepitch helical torque shoulder surface.
 2. The tubular connection ofclaim 1 wherein both (i) the first tapered constant pitch thread and thefirst variable pitch helical torque shoulder surface are sized andlocated relative to each other and (ii) the second tapered constantpitch thread and the second variable pitch helical torque shouldersurface are sized and located relative to each other, such that duringrotational make-up of the pin member and box member under control ofinteraction between the first tapered constant pitch thread and thesecond tapered constant pitch thread, the first variable pitch helicaltorque shoulder surface is guided into cooperating alignment with thesecond variable pitch helical torque shoulder surface.
 3. The tubularconnection of claim 2 wherein upon final make-up of the pin member andthe box member the first variable pitch helical torque shoulder surfaceis moved into wedged engagement with the second variable pitch helicaltorque shoulder surface.
 4. The tubular connection of claim 2 whereinupon final make-up of the pin member and the box member, the firstvariable pitch helical torque shoulder surface and second variable pitchhelical torque shoulder surface are engaged at a location that is one of(i) at a pin-nose/box-base location that intersects the inside diameterof the connection, (ii) at a pin-base/box-face location that intersectsthe outside diameter of the connection or (iii) at a middle-wall sectionof the connection as a center shoulder of the connection.
 5. The tubularconnection of claim 1 wherein the first variable pitch helical torqueshoulder surface and second variable pitch helical torque shouldersurface have a load flank lead greater than the stab flank lead.
 6. Thetubular connection of claim 1, wherein: a root diameter of the firstvariable pitch helical torque shoulder surface is smaller than both astarting root diameter of the first tapered constant pitch thread and anending root diameter of the first tapered constant pitch thread; a rootdiameter of the second variable pitch helical torque shoulder surface issmaller than both a starting root diameter of the second taperedconstant pitch thread and an ending root diameter of the second taperedconstant pitch thread.
 7. The tubular connection of claim 6 wherein: thepin member includes a first transition zone axially between the firstvariable pitch helical torque shoulder surface and the first taperedconstant pitch thread, the first transition zone including a first sealsurface; the box member includes a second transition zone axiallybetween the second variable pitch helical torque shoulder surface andthe second tapered constant pitch thread, the second transition zoneincluding a second seal surface; in full made up condition the firstseal surface engages the second seal surface for sealing.
 8. The tubularconnection of claim 7 wherein: an axial length of the first variablepitch helical torque shoulder surface is less than an axial length ofthe first tapered constant pitch thread; an axial length of the secondvariable pitch helical torque shoulder surface is less than an axiallength of the second tapered constant pitch thread.
 9. The tubularconnection of claim 8 wherein: the axial length of the first variablepitch helical torque shoulder surface is substantially less than theaxial length of the first tapered constant pitch thread; the axiallength of the second variable pitch helical torque shoulder surface issubstantially less than the axial length of the second tapered constantpitch thread.
 10. The tubular connection of claim 6 wherein: the firstvariable pitch helical torque shoulder surface extends for substantiallyfewer turns than does the first tapered constant pitch thread; thesecond variable pitch helical torque shoulder surface extends forsubstantially fewer turns than does the second tapered constant pitchthread.
 11. The tubular connection of claim 1 wherein the first variablepitch helical torque shoulder surface extends substantially to a firstsubstantially cylindrical torque shoulder surface of the pin member andthe second variable pitch helical torque shoulder surface extendssubstantially to a second substantially cylindrical torque shouldersurface of the box member, in full made-up position of the connectionthe first substantially cylindrical torque shoulder surface engages thesecond substantially cylindrical torque shoulder surface and the firstvariable pitch helical torque shoulder surface engages the secondvariable pitch helical torque shoulder surface, such that a combinedcylindrical and helical torque shoulder results.
 12. A tubularconnection, comprising: a pin member having: a first tapered constantpitch thread structure; a first variable pitch helical torque shouldersurface spaced axially along the pin member from the first threadstructure, wherein the first variable pitch helical torque shoulder isnon-tapered; a box member having: a second tapered constant pitch threadstructure; a second variable pitch helical torque shoulder surfacespaced axially along the box member from the second thread structure,wherein the second variable pitch helical torque shoulder isnon-tapered; wherein the first thread structure and the second threadstructure are sized and located to control a stab position of thetubular connection, in the stab position the first variable pitchhelical torque shoulder surface does not engage or overlap with thesecond variable pitch helical torque shoulder surface.
 13. The tubularconnection of claim 12 wherein the first variable pitch helical torqueshoulder surface and second variable pitch helical torque shouldersurface have a load flank lead greater than the stab flank lead.
 14. Thetubular connection of claim 12 wherein: both (i) the first threadstructure and the first variable pitch helical torque shoulder surfaceare sized and located relative to each other and (ii) the second threadstructure and the second variable pitch helical torque shoulder surfaceare sized and located relative to each other, such that duringrotational make-up of the pin member and box member under control ofinteraction between the first thread structure and the second threadstructure, the first variable pitch helical torque shoulder surface isguided into cooperating alignment with the second variable pitch helicaltorque shoulder surface.
 15. The tubular connection of claim 12 whereinthe first variable pitch helical torque shoulder surface extendssubstantially to a first substantially cylindrical torque shoulder ofthe pin member and the second variable pitch helical torque shouldersurface extends substantially to a second substantially cylindricaltorque shoulder of the box member, in full made-up position of theconnection the first substantially cylindrical torque shoulder engagesthe second substantially cylindrical torque shoulder and the firstvariable pitch helical torque shoulder surface engages the secondvariable pitch helical torque shoulder surface, such that a combinedcylindrical and helical torque shoulder results.
 16. A method of joiningtubular length of oil country tubular casing or piping, the methodcomprising: utilizing a first tubular member having an associated pinmember with a first tapered constant pitch thread structure and a firstnon-tapered variable pitch helical torque shoulder surface spacedaxially along the pin member from the first thread structure; utilizinga second tubular member having an associated box member with a secondtapered constant pitch thread structure and a second non-taperedvariable pitch helical torque shoulder surface spaced axially along thebox member from the second thread structure; engaging the pin member andbox member with each other into a stab position that is defined byinteraction of the first thread structure and the second threadstructure, in the stab position the first variable pitch helical torqueshoulder surface does not engage or overlap with the second variablepitch helical torque shoulder surface; rotating at least one of thefirst tubular member or the second tubular member such that interactionbetween the first thread structure and the second thread structureguides the first variable pitch helical torque shoulder surface intocooperating alignment with the second variable pitch helical torqueshoulder surface.
 17. The method of claim 16 including continuingrotation of at least one of the first tubular member or the secondtubular member until the first variable pitch helical torque shouldersurface wedges with the second variable pitch helical torque shouldersurface.
 18. The method of claim 17 wherein the pin member is formedintegral with the first tubular member and the box member is formedintegral with the second tubular member.